Process for the preparation of vinyltetrazole

ABSTRACT

Improved processes for the preparation of 1-and 2- alkyl-5vinyltetrazoles which involve the reaction of an ammonium azide and a Beta -dialkylaminopropionitrile in a water solvent and alkylating the product thereof under a carefully maintained pH.

United States Patent [191 Gilligan et a1.

[ 1 Feb. 13, 1973 PROCESS FOR THE PREPARATION OF VINYLTETRAZOLEInventors: William H. Gilligan, Washington, DC; Chilton H. McDonnell,Indian Head; Orlando Jones, Pisgah, both of Md.

Assignee: The United States of America as represented by the Secretaryof the Navy Filed: Oct. 29, 1969 Appl. No: 872,432

U.S. C1 ..260/308 D, 149/19, 260/705 Int. Cl. ..C07d 55/56 Field ofSearch ..260/308 D Primary Examiner-Leland A. Sebastian Att0rney-R. S.Sciascia and J. A. Cooke [57] ABSTRACT Improved processes for thepreparation of l-and 2- alkyl-S-vinyltetrazoles which involve thereaction of an ammonium azide and a B-dialkylaminopropionitrile in awater solvent and alkylating the product thereof under a carefullymaintained pH.

16 Claims, No Drawings PROCESS FOR THE PREPARATION OF VINYLTETRAZOLEBACKGROUND OF THE INVENTION 7 This invention relates generally toprocesses for the synthesis of l-and 2-alkyl-5-vinyltetrazoles and moreparticularly to improved processes for the synthesis of l-and2-methyl-S-vinyltetrazole, which are especially useful as monomermaterials from which high-nitrogen content polymeric binder propellantmaterials can be prepared.

The present state-of-the-art process for the synthesis of l-and2-alkyl-5-vinyltetrazoles involves generally the reaction of andialkylammonium azide with a B-dialkylaminopropionitrile in anon-aqueous solvent such as dimethylformamide (DMF). This initialreaction forms a 5-( B-dialkylaminoethyl) tetrazole. However, it isessential that the DMF solvent be removed completely since its presencecontaminates the final products. Since at this stage of the synthesisthe products are in a slurry form and since the DMF is a high boilingliquid, it is extremely difficult to remove all of it even under reducedpressure. In practice, it has been found that it is necessary todissolve the tetrazole and other salts in water and then extract thewater layer with methylene chloride to remove the last portions of theDMF. This total extraction process is obviously tedious and costly.

The aqueous solution of the 5-( B-dialkylaminoethyl) tetrazole is thenalkylated with a dialkylsulfate in the presence of sodium bicarbonate toform a mixture of land 2-alkyl-5-( B-trialkylammoniumalkyl) tetrazolewhich upon the application of heat forms a mixture of desired l-and2-alkyl-5-vinyltetrazoles. This mixture consists of approximately equalquantities of the two isomers which are separated by fractionaldistillation.

However, in large scale operations, great difficulties are encounteredin separating these isomers because of their very high boiling pointsand their strong tendency to polymerize. Moreover, sometimes it isdesirable to form a greater quantity of one of the isomers than theother. For example, in the case of l-and Z-methyl-S- vinyltetrazole, theZ-isomer is the more preferred monomer for binder applications and it istherefore usually the more desirable end product of the synthesis. Thepresent state-of-the-art synthesis of these materials as hereinbeforedescribed does not afford a procedure whereby the yields of these endproducts can be controlled.

SUMMARY OF THE INVENTION lt is therefore one object of the presentinvention to provide a process for the synthesis of l-and 2-alkyl-5-vinyltetrazoles.

Another object of the present invention is to provide a more simple andeconomical process for the synthesis of l-and 2-alkyl-5-vinyltetrazoles.

Still another object of this invention is to provide a process for thesynthesis of l-and 2-alkyl-5-vinyltetrazoles whereby the isomers aremore readily separated.

A further object of the present invention is to provide a process forthe synthesis of l-and 2-alkyl-5-vinyltetrazoles which allows for thecontrolof the yields of each of the isomers and thereby affords greateryeilds of the more desirable isomer.

Finally, it is an object of this invention to provide a process for thesynthesis of l-and Z-alkyl-S-vinyltetrazoles which provides for higheryields of each isomer than heretofore attained.

These and other objects are accomplished by providing a process whereinthe l-and 2-alkyl-5-vinyltetrazoles are completely prepared in aqueoussolution with control of the pH of the reaction mixture during thealkylation step and with the further control of the quantities ofalkylating agent employed.

DESCRIPTION OF THE PREFERRED EMBODlMENTS In one embodiment ofthisinventiomthe improved process involves the reaction of aB-dialkylaminopropionitrile with an ammonium or alkylammonium ordialkylammonium azide, preferably in stoichiometric amounts, in aqueoussolution at reflux temperature to form a 5-( B-dialkylaminoethyl)tetrazole. The quantity of water solvent is not critical, however it ispreferred that the reaction solution be concentrated. Although theammonium, alkyl or dialkyl ammonium azide may be added to theB-dialkylaminopropionitrile as a preformed material, preferably it isformed in situ by the addition and reaction of a metal inorganic azidesuch as sodium or potassium and an ammonium, alkyl or dialkylammoniumsalt such as a chloride, bromide or sulfate, etc. For more economicalpurposes, it may be desirable to per-form this initial reaction of thepresent invention simply using a B-dialkylaminopropionitrilehydrochloride and an inorganic azide in aqueous solvent as startingmaterials. Therefore, among the starting materials which are encompassedwithin the scope of this invention are for example,B-dimethylaminopropionitrile, B- diethylaminopropionitrile, B-dipropylaminopropionitrile, ammonium azide, dimethylammonium azide,diethylammonium azide, B-

dimethylaminopropionitrile hydrochloride, B- diethylaminopropionitrilehydrochloride B- dipropylaminopropionitrile hydrochloride, sodium azide,potassium azide and the like. The effective use of water as the solventduring this initial reaction step is a surprising result since normallythe reaction of azide ion with a nitrile in aqueous solution does notoccur unless the nitrile group is activated by electronegativesubstituents. The employment of water as the solvent material, nowobviously eliminates the burden of extracting deleterious solvents suchas dimethylformamide at this point and eliminates the hazard ofcontamination of the final products due to these harmful solvents andthereby aids in the result of higher yields of the end products. Incontinuing the preparation, additional water (enough to effect solution)is added to the reaction mixture and the 5.-( B-dialkylaminoethyl)tetrazole is alkylated, employing about 1.5 to 2 or more equivalents ofan alkylating agent, under a predetermined and carefully controlled pHcondition. Any of the known alkylating agents may be employed for thepurposes of this invention, but preferably the dialkylsulfates, such asdimethy-lsulfate, diethylsulfate and dipropylsulfate, are used. Afterrefluxing for about 2 hours, still under carefully controlled pHconditions, the mixture of the l-and 2-alkyl-5-vinyltetrazoles isextracted from the reaction mixture using-a suitable sol vent such asmethylene chloride, ether, chloroform, etc. and are separated byconventional fractional distillation methods. It has been surprisinglydiscovered that by the selective determination and control of the pH ofthe reaction mixture during the alkylation step higher yields of one orthe other alkyl--vinyltetrazole isomer is obtained. For example, if thealkylation reaction step is run at a specific pH in the range of fromabout 4 to about 1 1 high yields of the 2-isomer are realized, while apH of below about 4 will result in greater yields of the l-isomer. Tablel below is an illustration of the effect of various pH conditions of thereaction mixture during the methylation, employing dimethylsulfate, of5-( B- dimethylaminoethyl) tetrazole in the present synthesis of l-and2-metl1yl-5-vinyltetrazoles..

TABLE! Methylation of 5-( B-dimethylaminoethyl) tetrazole at various pHsyield pH l-methyl-S-vinyl 2-methyl-5-vinyl tetrazole tetrazole l0.5 2862 8.3 32 64 8.1 33 65 7.2 39 6| 6.0 44 52 4.0 27 64 2.0 49 3 Thecontrol of the pH of the reaction mixture during alkylation may beperformed by any of the conventional methods known within the art. Forexample when basic conditions are desired, NaOH or any other compatiblehydroxide ion material may be employed and the pH is observed with a pHmeter. The sole use of NaHCO to afford basic conditions is not desirablesince it is not a strong enough base to adjust for the acid conditionswhich result after the addition of the alkylating agent, likedimethylsulfate. However, sodium bicarbonate (NaHCO may be used incombination with another compatible basic material, such as sodiumcarbonate (NaCO Another embodiment of this invention, utilizes theunexpected discovery that if the amount. of alkylating agent is alsocontrolled during the alkylation step of the present process, theresulting tetrazole isomers are selectively formed and thereby areseparated without the burdens of fractional distillation. Thisphenomenon is a result of the discovery that the rate of alkylation ofthe l-isomer is very much faster than'the rate of alkylation of the2-isomer. Thus, the isomers can be separated by a two-step alkylationprocedure. There-- fore, when the alkylation procedure is performed withthe addition of 1.5 equivalents of the alkylating agent to theS-(B-dialkylaminoethyl) tetrazole and refluxed for about 2hours,essentially all of the l-alkyl-5-vi'nyltetrazole isomer is obtained andmay be extracted with e.g. methylene chloride. After the extraction ofthe lisomer, an excess of alkylating agent (i.e. 0.5 equivalents ormore) is added to the remaining aqueous solution still under controlledpH conditions and again refluxed for about 2 hours upon whichessentially all of the 2-isomer is obtained and again easily extractedby solvent techniques.

The general nature of the invention having been set forth, the followingexamples are presented as specific ble to various modifications thatwill be recognized by v one of ordinary skill in the art.

Preparation ofl and 2-alkyl-5 -vinyltetrazole EXAMPLE I To. 0.2 mole ofdimethylaminopropionitrile was added dropwise 16.43 ml of'concentratedhydrochloric acid at ice-bath temperature. After adding l4.3g (0.22mole) of sodium azide the slurry was refluxed for 6 hrs. with stirring.After cooling, 200 ml of water and 17g of sodium bicarbonate .was addedand the pH was ad justed to 8.5 with l2N NaOH. The solution was thenmethylated with 50 ml of dimethylsulfate at 10 :2 holding the pH at 8.5$0.3 by the addition of l2N NaOH as required. The solution was stirredat pH 8.5 for 2 hr. after the addition was completed. The solution wasthen refluxed for 2 hours, cooled, and extracted with 5 l50 ml methylenechloride. After drying with magnesium sulfate and filtering, thesolventwas removed in vacuo to have 16.5g percent) of l andZ-Methyl-S-viriylte-trazole. The as indicated by GLC.

EXAMPL'EI'IN stirring to a solution of 4l.0g (0.42 mole) ofdimethylaminopropionitrile and 37.5g- (0.46 mole) of dimethylaminehydrochloride in 21 ml of water. This solution was refluxed (lll-l20)for 23 hrs. while passing a slow stream of nitrogen over the surface ofthe solution. Before complete cooling 450 ml of water was added withstirring and 40g of sodium bicarbonate dissolved in the clear redsolution. The pH was adjusted to 8.4 with l2N NaOH and the solution wasthen methylated with ml of dimethylsulfate over a period of 1 hr. whilethe pH was held at 8.4 :L0.l by the addition of l2N sodium hydroxide andthe temperature at 27 :1 by intermittent cooling. The solution was thenstirred for 2 hours while holding the pH at 8.4.

'After the addition of 0.5g of trinitrobenzene (as a polymerizationinhibitor) the solution .was refluxed for 2 hrs., cooled and extractedwith 6 X 250 ml of methylene chloride. After drying thecombined'extracts with anhydrous magnesium sulfate and filtering, thesolvent was removed in vacuo to yield 36.9g (80 percent) of 1 and2-methyl-5-vinyltetrazole. The product analyzed 97%+ by GLC.

Effect of pH During methylation on the lsom'er Ratio EXAMPLE III a. Ph4.0. The pH ofa solution of4.36g (0.031 mole) ofS-(B-dimethylaminoethyl) tetrazole in 37 ml of water was adjusted to 4.0with concentrated sulfuric acid. Then, 7.5 ml (0.08 mole) of dimethylsulfate was added dripwise over a period of 1 hour. During themethylation the pH was held at 4.0 $0.2 by the addition of 6N sodiumhydroxide as required and the temperature at 24 :1 by intermittentcooling with an ice bath. After the addition of the dimethyl sulfate,the solution was stirred for 30 minutes and then the pH was adjusted to8.5 with solid sodium hydroxide. After adding 50 mg of trinitrobenzene,the-solution was refluxed'for 2 hours, cooled and extracted with j 5 X 7ml purity was 99 percent+ methylene chloride. After drying the extractwith anhydrous magnesium sulfate and filtering the solvent was removedin vacuo.

The weight of the product was 3.1g (91 percent). The product wasessentially pure by GLC analysis and showed a ratio of2-methyl-5-vinyltetrazole to lmethyl-S-vinyltetrazole of 2.43:1.

b. pH 8.3. Method same as (a) above except that the pH was held at 8.310.2 by the addition of 6N NaOH as required during the methylation. Theyield of product was 3.3lg (97 percent). The purity was 99%+ asindicated byGLC analysis and the ratio of 2-methyl-5- vinyltetrazole tol-methyl-5-vinyltetrazole was 2.1 :1.

' c. pH 2.0. Method same as (a) above except that the pH duringmethylation was held at 2.0 10.2 by the addition of concentratedsulfuric acid is required. The yield of product was 52 percent with aratio of 2-isomer to 1 ofl:l5.l.

Selective Separation of l-alkyl and 2-alkyl-5- vinyltetrazole EXAMPLE IVThe pH of a solution of 4.36g (0.031 mole) of S-(BB- dimethylaminoethyl)tetrazole and 2.87g (0.035 mole) of sodium acetate in 37 ml of water wasadjusted to pH 6.0 with 12N sulfuric acid. The solution was methylatedwith 5 ml (1.5 equiv. of dimethylsulfate over a period of 1 hour. Duringthe methylation the pH was maintained at 6.0 $0.1 by the addition of 12Nsodium hydroxide and the temperature was held at 25 :L-l". After theaddition of the sulfate the solution was stirred for 2 hours at pH 6.0.The pH was then readjusted to 8.4, 50 mg of trinitrobenzene was addedand the solution refluxed for 2 hours.

The yield of product after isolation in the usual fashion was 1.55g (45percent corr.). The purity was 97 percent by GLC analysis and consistedof 42 percent of 1-methyl-5-vinyltetrazole and 3.2 percent of Z-methyl-S-vinyltetrazole.

The aqueous solution from the above methylation was methylated with anadditional 3ml of dimethylsulfate under the same conditions. Anadditional 1.72g (51 percent) of product was obtained. GLC analysisshowed 49 percent of 2-methyl-5-vinyltetrazole and 2 percent ofl-methyl-S-vinyltetrazole.

We claim:

1. A process for synthesizing a mixture of 1- and 2- alkyl-5-vinyltetrazoles wherein either the 1- or 2- isomer predominates whichcomprises reacting a B- lower-dialkylaminopropionitrile wherein saidlower-dialkyl is selected from the group consisting of dimethyl, diethyland dipropyl with an azide compound selected from the group consistingof ammonium azide, a loweralkylammonium azide and alower-dialkylammonium azide in an aqueous solvent, alkylating theproduct thereof in an aqueous solvent under a controlled pH of fromeither about 4 to about 1 1 if an excess of the 2- isomer is desired orbelow about 4 but greater than about 2 if an excess of the 1 isomer isdesired, wherein the alkylating step is performed by the addition andreaction of a dialkylsulfate; and refluxing the alkylated products.

2. The process of claim 1 wherein said azide compound is formed in situby the reaction of a metal inorganic azide compound selected from thegroup consisting of an alkali metal azide and an alkaline earth metalazide with a compound selected from the group consisting of an ammoniumsalt, a lower-alkylammonium salt and a lower-dialkylammonium salt.

3. The process of claim 1 wherein said alkylating is performed by theaddition and reaction of an alkylating agent selected from the groupconsisting of dimethylsulfate, diethylsulfate and dipropylsulfate.

4. The process of claim 1 wherein saidB-lower-dialkyl-aminopropionitrile is [3- dimethylaminopropionitrile,said lower-dialkylammonium azide is dimethylammonium azide and saidalkylating is performed by the addition and reaction of dimethylsulfate.

5. The process of claim 1 wherein said pH during alkylation is withinthe range of from about 41 1 thereby allowing a higher yield of the2-alkyl-5-vinyltetrazole isomer than the l-alkyl-S-vinyltetrazoleisomer.

6. The process of claim 1 wherein said pH during alkylation is less than4 thereby allowing a higher yield of the l-alkyl-S-vinyltetrazole isomerthan the 2-alkyl-5- vinyltetrazole isomer.

7. A process for synthesizing a mixture of 1- and 2-alkyl-5-vinyltetrazoles wherein either the 1- or 2- isomer predominateswhich comprises reacting a [3- lower-dialkylaminopropionitrilehydrochloride wherein said lower-dialkyl is selected from the groupconsisting of dimethyl, diethyl and dipropyl with a metal inorganicazide selected from the group consisting of an alkali metal azide and analkaline earth metal azide in an aqueous solvent, alkylating the productthereof in an aqueous solvent under a controlled pH of from either about4 to about 11 if an excess of the 2- isomer is desired or below about 4but greater than about 2 if an excess of the l-isomer is desired whereinthe alkylating step -is performed by the addition and reaction of adialkylsulfate; and refluxing the alkylated products.

8. The process of claim 7 wherein said pH during alkylation is withinthe range of from about 4-1 1 thereby allowing a higher yield of the2-alkyl-5-vinyltetrazole isomer than the l-alkyl-5-vinyltetrazoleisomer.

9. The process of claim 7 wherein said pH during alkylation is less than4 thereby allowing a higher yield of the l-alkyl-S-vinyltetrazole isomerthan the 2-alkyl-5- vinyltetrazole isomer.

10. A process for synthesizing and separating 1- and2-alkyl-5-vinyltetrazole which comprises the steps of:

1. reacting a B-lower-dialkylaminopropionitrile selected from the groupconsisting of B- dimethylaminopropionitrile, B-diethylaminopropionitrile and B- dipropylaminopropionitrile with anazide compound selected from the group consisting of ammonium azide, alower-alkylammonium azide and a lowerdialkylammonium azide in an aqueoussolvent,

. adding to and reacting with the product of step (1 under a controlledpH within the range of from about 2 to about 1 1 about 1.5 equivalentsof an alkylating agent selected from the group consisting ofdimethylsulfate, diethylsulfate and dipropylsulfate and refluxing toform the respective 1- alkyl-S-vinyltetrazole isomer,

3. extracting said Lalkyl-S-vinyltetrazole isomer and adding to andreacting with the remaining aqueous solution, under a controlled pHwithin the range of from about 2 to about 11, 0.5 or more equivalents ofsaid alkylating agent and refluxing to form the respective2-alkyl-5-vinyltetrazole isomer and,

4. extracting said 2-alkyl-5-vinyltetrazole isomer.

11. The process of claim wherein said azide compound is formed in situby the reaction of a metal azide compound selected from the groupconsisting of an alkali metal azide and an alkaline earth metal azidewith a compound selected from the group consisting of an ammonium salt,a lower-alkylammonium salt and a lower-dialkylammonium salt.

12. The process of claim 10 wherein said controlled pH in steps 2 and 3is within the range of from about 4 to about 1 l.

13. The process of claim 10 wherein said controlled pH in steps 2 and 3is less than 4.

14. A process for synthesizing and separating 1- and2-alkyl-5-vinyltetrazole which comprises the steps of:

l. reacting a B-lower-dialkylaminopropionitrile hydrochloride selectedfrom the group consisting of fi-dimethylaminopropionitrilehydrochloride, [3- diethylpropionitrile hydrochloride andB-dipropylpropionitrile hydrochloride with a metal inorganic azideselected from the group consisting of analkali metal azide and analkaline earth metal azide in an aqueous solvent,

. adding to and reacting with the product of step 1) under a controlledpH within the range of from about 2 to about I 1 about l.5 equivalentsof an alkylating agent selected from the group consisting ofdimethylsulfate, diethylsulfate and dipropylsulfate and refluxing toform the respective lalkyl-S-vinyltetrazole isomer,

3. extracting said l-alkyl-S-vinyltetrazole isomer and adding to andreacting with the remaining aqueous solution under a controlled pHwithin the range of from about 2 to about I l, 0.5 or more equivalentsof said alkylating agent and refluxing to form the respective2-alkyl-5-vinyltetrazole isomer and,

4. extracting said 2-alkyl-5-vinyltetrazole isomer.

15. The process of claim 14 wherein said controlled pH in steps 2 and 3is within the range of from about 4 to about l1.

16. The process of claim 14 wherein said controlled pH in steps 2 and 3is less than 4.

1. A process for synthesizing a mixture of 1- and 2-alkyl-5-vinyltetrazoles wherein either the 1- or 2- isomer predominates whichcomprises reacting a Beta -lower-dialkylaminopropionitrile wherein saidlower-dialkyl is selected from the group consisting of dimethyl, diethyland dipropyl with an azide compound selected from the group consistingof ammonium azide, a lower-alkylammonium azide and alower-dialkylammonium azide in an aqueous solvent, alkylating theproduct thereof in an aqueous solvent under a controlled pH of fromeither about 4 to about 11 if an excess of the 2-isomer is desired orbelow about 4 but greater than about 2 if an excess of the 1 isomer isdesired, wherein the alkylating step is performed by the addition andreaction of a dialkylsulfate; and refluxing the alkylated products. 1.reacting a Beta -lower-dialkylaminopropionitrile selected from the groupconsisting of Beta -dimethylaminopropionitrile, Beta-diethylaminopropionitrile and Beta -dipropylaminopropionitrile with anazide compound selected from the group consisting of ammonium azide, alower-alkylammonium azide and a lower-dialkylammonium azide in anaqueous solvent,
 1. reacting a Beta -lower-dialkylaminopropionitrilehydrochloride selected from the group consisting of Beta-dimethylaminopropionitrile hydrochloride, Beta -diethylpropionitrilehydrochloride and Beta -dipropylpropionitrile hydrochloride with a metalinorganic azide selected from the group consisting of an alkali metalazide and an alkaline earth metal azide in an aqueous solvent,
 2. addingto and reacting with the product of step (1) under a controlled pHwithin the range of from about 2 to about 11 about 1.5 equivalents of analkylating agent selected from the group consisting of dimethylsulfate,diethylsulfate and dipropylsulfate and refluxing to form the respective1-alkyl-5-vinyltetrazole isomer,
 2. adding to and reacting with theproduct of step (1) under a controlled pH within the range of from about2 to about 11 about 1.5 equivalents of an alkylating agent selected fromthe group consisting of dimethylsulfate, diethylsulfate anddipropylsulfate and refluxing to form the respective1-alkyl-5-vinyltetrazole isomer,
 2. The process of claim 1 wherein saidazide compound is formed in situ by the reaction of a metal inorganicazide compound selected from the group consisting of an alkali metalazide and an alkaline earth metal azide with a compound selected fromthe group consisting of an ammonium salt, a lower-alkylammonium salt anda lower-dialkylammonium salt.
 3. The process of claim 1 wherein saidalkylating is performed by the addition and reaction of an alkylatingagent selected from the group consisting of dimethylsulfate,diethylsulfate and dipropylsulfate.
 3. extracting said1-alkyl-5-vinyltetrazole isomer and adding to and reacting with theremaining aqueous solution under a controlled pH within the range offrom about 2 to about 11, 0.5 or more equivalents of said alkylatingagent and refluxing to form the respective 2-alkyl-5-vinyltetrazoleisomer and,
 3. extracting said 1-alkyl-5-vinyltetrazole isomer andadding to and reacting with the remaining aqueous solution, under acontrolled pH within the range of from about 2 to about 11, 0.5 or moreequivalents of said alkylating agent and refluxing to form therespective 2-alkyl-5-vinyltetrazole isomer and,
 4. extracting said2-alkyl-5-vinyltetrazole isomer.
 4. extracting said2-alkyl-5-vinyltetrazole isomer.
 4. The process of claim 1 wherein saidBeta -lower-dialkyl-aminopropionitrile is Beta-dimethylaminopropionitrile, said lower-dialkylammonium azide isdimethylammonium azide and said alkylating is performed by the additionand reaction of dimethylsulfate.
 5. The process of claim 1 wherein saidpH during alkylation is within the range of from about 4-11 therebyallowing a higher yield of the 2-alkyl-5-vinyltetrazole isomer than the1-alkyl-5-vinyltetrazole isomer.
 6. The process of claim 1 wherein saidpH during alkylation is less than 4 thereby allowing a higher yield ofthe 1-alkyl-5-vinyltetrazole isomer than the 2-alkyl-5-vinyltetrazoleisomer.
 7. A process for synthesizing a mixture of 1- and2-alkyl-5-vinyltetrazoles wherein either the 1- or 2- isomerpredominates which comprises reacting a Beta-lower-dialkylaminopropionitrile hydrochloride wherein saidlower-dialkyl is selected from the group consisting of dimethyl, diethyland dipropyl with a metal inorganic azide selected from the groupconsisting of an alkali metal azide and an alkaline earth metal azide inan aqueous solvent, alkylating the product thereof in an aqueous solventunder a controlled pH of from either about 4 to about 11 if an excess ofthe 2-isomer is desired or below about 4 but greater than about 2 if anexcess of the 1-isomer is desired wherein the alkylating step isperformed by the aDdition and reaction of a dialkylsulfate; andrefluxing the alkylated products.
 8. The process of claim 7 wherein saidpH during alkylation is within the range of from about 4-11 therebyallowing a higher yield of the 2-alkyl-5-vinyltetrazole isomer than the1-alkyl-5-vinyltetrazole isomer.
 9. The process of claim 7 wherein saidpH during alkylation is less than 4 thereby allowing a higher yield ofthe 1-alkyl-5-vinyltetrazole isomer than the 2-alkyl-5-vinyltetrazoleisomer.
 10. A process for synthesizing and separating 1- and2-alkyl-5-vinyltetrazole which comprises the steps of:
 11. The processof claim 10 wherein said azide compound is formed in situ by thereaction of a metal azide compound selected from the group consisting ofan alkali metal azide and an alkaline earth metal azide with a compoundselected from the group consisting of an ammonium salt, alower-alkylammonium salt and a lower-dialkylammonium salt.
 12. Theprocess of claim 10 wherein said controlled pH in steps 2 and 3 iswithin the range of from about 4 to about
 11. 13. The process of claim10 wherein said controlled pH in steps 2 and 3 is less than
 4. 14. Aprocess for synthesizing and separating 1- and 2-alkyl-5-vinyltetrazolewhich comprises the steps of:
 15. The process of claim 14 wherein saidcontrolled pH in steps 2 and 3 is within the range of from about 4 toabout 11.